SOL-Perpetua™ Solar Water Heating System Installation Instructions and Operating Manual For Series "A" Pumps
SOL Perpetua™ System Troubleshooting - Mushroom Valve Leak
This valve is air tight so long as there is no dirt under it. Because of its shape it is called an "mushroom" valve. It works together with the valve in the hand pump to establish a vacuum in the system. When the shutoff cock next to it is open, it relieves fluid and vapour if the temperature in the bubble pump becomes about 105C (221 F).
With your (clean) fingernails remove the valve. Pick out any bits of dirt that may be stuck on the brass seat and wipe the surface clean. Wipe the underside of the valve clean, apply clean vacuum grease to the brass seat and the underside of the valve and push the valve back in place. This last act may take a few trys because it's all so slippery. Note: It is essential that you not reintroduce dirt under the valve; a tiny hair or lint lying on the brass seating of the valve will cause a leak. Use the vacuum grease as provided with your order. If you lose it, you may use Vaseline.